Self-centering grinding system particularly suitable for the finishing and repair of large crankshafts



SELYUENTERING GRINDING SYSTEM PARTICULARLY SUITABLE POB THB PINISHING AND REPAIR OF LARGE CRANKSHAFTS A. VENESIA July 22, 1969 5 `Sheets-Sheet. 1

INVENTOR rr/Ja wfg/4 Filnd March 10, 1966 ATTORNEY A. vENEslA l 5 Sheets-Sheet 2 INVENTOR ATTORNEY July 22, 1969 SELF-CENTEH1NG GRINDING SYSTEM PARTICULARLY SUITABLE FOR THE FINISHING AND REPAIR 0F LARGE CRANKSHAFTS Filed March l0. 1966 U4 il l @i July 22, 1969 A. vENEslA 3,456,391

SELF-GENI'ERING @BINDING SYSTEM PARTICULARLY SUITABLE Fon 'rms FINISHING AND REPAIR oF LARGE cRANKsHAFTs 3 Sheets-Sheet 5 Filed latch 10, 1966 OR iff/V550# BY Mic www ATTQRNEY SELF-CENTERING GRINDING SYSTEM PARTICU- f' LARLY SUITABLE FOR THE FINISHING AND REPAIR OF LARGE CRANKSHAFTS y Y Attilio Venesia, corso Ferrucci 96, Turin, Italy Filed Mar. 10, 1966, Ser. No. 533,158 Claims priority, application Italy, Mar. 20, 1965, 6,586/ 65 Int. Cl. B24b 5/22, 5/42 U.S. Cl. 51-55 6 Claims ABSTRACT F THE DISCLOSURE Apparatus for grinding of large crankshafts characterized by including a split ring type frame having centerless support rollers on radii at 90 .angles to each other, with the axis of a at faced grinding disc being on a radius midway of said radii.

The grinding of large shafts, especially the crankshafts of large engines, steam engines, compressors, presses and similar machines, which frequently reach the weight of several tens of tons, constitutes a grave problem in the case of their construction, and an even graver problem when repairs are necessary since this generally requires a grinding operation to re-establish the cylindricality of their bearings, particularly those of the connecting rods.

In fact such repairs are generally carried out -by prior dismantling followed by grinding with a large grinding machine and final reassembly. Apart from the expenses thus incurred, the fact that the plant served by the engine (e.g. a ship) is out of service for some time must be taken into account.

Again the grinding machinery which has only a limited range of use, must often remain idle kand represents capital tied-up with a poor rate of return.

The present invention is intended to remove such inconveniences and comprises a new system of centreless grinding which provided for equipment capable of grinding eccentric bearings, of connecting rods for example, without it being necessary to dismantle the shaft of the relevant machine, thus reducing the operation to the level of a maintenance operation so that, in the case of a ship, for example, the work may be carried out during a normal discharging or turn-round period without unnecessary loss of use of the same.

The grinding equipment which is the object of the invention also presents notable advantages in the grinding of the carrying or main bearings, of the shaft, which normally necessitates the removal of the shaft from the machine. With the said equipment, however, they can be ground by a large, common lathe which can be used for other purposes between one such grinding and the next.

The technical principle on which the present invention is based is that a rounded, oval body revolving on two points, which make an angle of less than 180 (in practice, as near 90 as possible) between them can be ground by means of a grinding wheel (usually of the cup type) placed, between the two points `and be made exactly cylindrical when the grinding wheel is moved forwards so that the diameter of its line of action passes through a point which with the two points on which the body revolves, describes a circle corresponding to the circumference of the body.

In practical terms, the grinding device, which embodies the said principle, is able to remove 4the protuberances on the body that is, those which have not been removed as a result of wear, and thus reduce the diameter to that corresponding to the maximum distance between the various worn sections.

The technical principle is, according to the invention,

"ice

embodied in an equipment which is relatively simple and .of low cost. Being easily movable it can be brought to the shaft tofbe worked, the big ends of the connecting rods having rst of all been substantially disassembled by removing the lower element of the connecting rod and by lwithdrawing the corresponding upper part andthe piston rod to the highest point in the cylinder. The grinding apparatus is then engaged on the bearing which is to be ground, the crankshaft itself being slowly turned while the operation is being carried out.

The same equipment, or one essentially similar, can be used for the grinding of main bearings in conjunction with a large lathe, as has been stated. This operation, however, although requiring the removal of the shaft from its machine or motor, is not of such a serious character since it does not need a special machine. Nor is it such a frequent operation as the grinding of big end bearings and can therefore be done in the occasion of a ret (e.g. of a ship) or when an engine is being reconditioned.

The accompanying drawings show, by way of nonlimiting example, one form of embodiment of the invention.

FIGURES 1 and 2 show the technical principle, schematically.

FIGURE 3 shows, in lateral elevation an equipment suitable for grinding, on a lathe, the main bearings of a crankshaft.

FIGURE 4 shows an analogous equipment for grinding, on a lathe, the big end bearings of a crankshaft.

FIGURE 5 shows, in plan view and on a larger scale .an equipment similar to that shown in FIG. 4.

FIGURE 6 is a section made along the plane VI-VI of FIG. 5.

FIGURE 7 shows the method of application of the said equipment to a large engine so as to be able to grind the big end bearings directly without dismantling the crankshaft.

With reference to the drawings, at 1 is shown the piece to be ground, a big end bearing for example, the said bearing having, as a result of wear caused by the connecting rod, some areas of reduced diameter 1' and, in consequence, some areas having the form of protuberances 1". The bearing 1 rests on support rollers 2 which are placed so as to form an angle of about with respect to the centre of the lbearing.

Between the said rollers 2 there is placed a grinding Wheel 3, preferably of the cup type, the line of abrasive action of which makes a third point of contact on the circumference of the bearing which is to be ground. The said grinding wheel, besides its normal rotary movement along the line of abrasive action, is able to be moved towards the piece to be ground, the effective extent of such movement ranging from the first point of contact with the said piece to the point at which the line of abrasive action passes through a circle the circumference of which is determined by the diameter to which the piece is to be ground, the points of lcontact of the two rollers 2 being also located on the same circumference.

In FIG. 6 a practical example of an assembly for grinding is shown. In this ligure the bearing to be ground is abig end Ibearing against which press two rollers 2, these being adjustable and mounted on a frame 4, which also carries the supports 5 for other rollers 5 which are pushed against the bearing 1 by springs 7 and only have the task of centering the device by acting in opposition to the rollers 2.

The frame 4 also carries a support 6 in which the shaft of the grinding Wheel 3 is mounted.

This shaft is provided with known means (not illustrated) to regulate the fom/ard movement of the wheel 3 towards the bearing :1, said means leading to a control wheel 8, and to a pulley 9 and a belt 10 driven by an electric motor 11 which is mounted on an auxiliary support 6 xed to the support 6. This group is connected to the piston rod 12 of a pneumatic or hydraulic cylinder 13 by means of which the Whole assembly of the frame 4 and the elements connected thereto can be moved forwards and backwards in correspondance with the slow rotary movement of the crankshaft on the bearing 1 of which the grinding device is mounted. For this purpose the cylinder 13 is mounted on its own support 14 by means of pins 15 and thus the whole grinding assembly can take up the different inclinations which are required owing to the movement of the crankshaft, in relation to which the said assembly in fact acts like a connecting rod.

To carry out the grinding, the bearing 1 is kept against the rollers 2 while the crankshaft turns slowly. The grinding wheel 3 is made to move towards the shaft while the grinding assembly, the support 14 of which is slidably mounted in the xed support 16 and is controlled by a screw 17 with a worm wheel 17 and a control wheel 18, carries out a side to side movement, as indicated by the arrow A (FIG. so that the grinding wheel 3 travels along the whole length of the bearing. Inv this way the grinding wheel removes any protuberances which are due to wear or, in the case of a new crankshaft, to imperfect manufacture.

In FIG. 4 the bearing 1 and the grinding assembly are mounted on a lathe, the former being .mounted between the centers and held on the lathe bed by suitable rests, while the apparatus is mounted on the carriage (or on one of the carriages) of the lathe by means of the support 14 so that it can work on the bearing 1 which is supported by the rollers 2, 5.

A similar form of assembly also permits the lathe grinding of main bearings (FIG. 3). In this case, however, the oscillating action similar to that of a connecting rod is not required and therefore it is not necessary that there should be a hydraulic or a pneumatic cylinder l13 nor, if the lathe is suciently precision-built, is there any need for a frame 4 or the parts connected therewith.

FIG. 7 shows the most satisfactory and most advan- Vtageous form of embodiment of the invention and deals with the grinding of a big end bearing of a very large diesel engine; in order to carry out this operation the lateral frame covers, which such engines commonly have to permit access to the connecting rods, are removed.

Then the big end itself is removed and the piston rod and the connecting rod are transferred to the upper part of the cylinder. The bearing is now completely accessible and the frame 4 with the two groups of rollers 2, 5 is mounted on it.

The support 14 is attached laterally to the engine frame and the operation can be carried out as already described.

In some large engines it is possible to obtain access to the main bearings and, in this case also, by removing the bearing covers it is possible to grind each main bearing in turn without dismantling the engine. However this operation is less frequently required than the former and can be therefore one, and Iby no means the longest, of the several operations which are carried out at a ret.

Lastly it should be noted that, with the system according to the invention, it is not necessary to apply a counterweight to the crankshaft since this rotates in a normal way. Where the bearing which is to be ground rotates about its own centre counterweights are needed,v but according to the invention the rotation takes place about the axis of the crankshaft itself.

- What I claim is:

1. In apparatus for grinding a large cylinder, comprising a main frame, a split frame pivotally mounted on said main frame for surrounding, and transverse to the axis of, the cylinder; and aflat faced axially rotatable grinding disc adjustably carried'by the split` fralme` and arranged with its axis of rotation :onta radius' of the cylinder; and its flat face perpendicular to lsuch radius of the cylinder; and traversing means for traversing the split frame and disc in a `direction perpendicular: to the rotational axis af the `disc and parallel to the cylinder axis so that the disc moves along the generating line of the cylinder then engaged by the disc; and means'for adjustably biasing the disc along its own axis of rotation towards the cylinder; the improvement which 'comprises two centerless support rollers vcarried by and inside of the split frame and engaging the cylinder and adpacent the disc, with such support rollers being spaced on radii of the cylinder apart, with these radii defining an angle bisected by theaxis of rotation of the grinding disc, whereby the three pointsof engagement of. the cylinder with the grinding disc and the two support rollers, when viewed endwise of the cylinder, define a circle of a circumference based on the eventual diameter of the cylinder when ground, and which is centered on the axis of the cylinder. l

2. In apparatus as described in claim 1; the improvement wherein the said traversing means and said biasing means are both carried by said main frame.

3. In apparatus as described in claim 2, the improvement wherein said split frame also carries two spring biased centerless opposition rollers arranged in opposition to the first named support rollers, and at the side of the cylinder remote from the disc and support rollers.

4. In apparatus as described in claim 2, said Ibiasing means comprising a hydraulic piston-cylinder means supporting said split frame and biasing it and parts carried by it against the cylinder being ground.

5. In apparatus as described in claim 4, the improvement wherein the piston-cylinder means is itself mounted to move longitudinally of the cylinder being ground so as to move the split frame also longitudinally of such cylinder.

6. In apparatus as described in claim 5, the inclusion of control means for adjustaably moving the pistoncylinder means longitudinally.

References Cited UNITED STATES PATENTS Geiten '51-241 X ROBERT C. RIORDON, Primary Examiner D. G. KELLY, Assistant Examiner U.S. Cl. X.R. v 51-126, 131, 241 

